The invention relates to a filter insert having a blocked shape configuration.
A filter insert disclosed in U.S. Pat. No. 3,531,920 has a block shape and is composed of a filter element that is pleated in a zigzag pattern. Mutually parallel dimples project from the pleat walls, with the dimples projecting from the plane of the pleat walls on both sides of the pleat walls and the dimples of adjacent pleat walls lying against one another at their contacting faces. Each one of the dimples extending perpendicularly to the edges of the zigzag pleats forming the crease has a height that gradually increases and decreases in the direction of movement of the medium and a width that increases in the direction of increasing height. Each pair of dimples that are adjacent within the pleat wall extend in mutually opposite directions with respect to the plane of the pleat wall; they are thus embossed to be raised and recessed, respectively.
The dimples are here arranged in such a way that each raised dimple in the pleat wall has an associated likewise raised, embossed dimple in the adjacent pleat wall in such a way that the zigzag pleat causes the associated dimples to lie on top of one another and to support one another in the region of their contacting faces.
In this way a space is ensured between the adjacent pleat walls which uniformly decreases in the direction of movement of the medium and uniformly increases after passage of the medium through the wall.
The drawback is here that the width of the dimples increases and decreases in the direction of movement of the medium so that the direction of flow of the medium to be filtered is deflected laterally. This increases flow resistance and requires greater conveying power for the medium to be filtered. With the increasing width of the dimples, the surface area available in the region of the wall for passage of the medium to be filtered is also reduced.
Moreover, the width of a channel for the medium formed between two adjacent dimples increases in the direction of movement of the medium. The change in cross section caused thereby additionally increases flow resistance in an undesirable manner. In order, to make the filtering of large quantities of a medium economically feasible, the energy to be made available for the filtering process should be as low as possible, particularly since the corresponding drive means generate more noise with increasing power.